Process for flameproofing cellulosic textile material



United States Patent This application is a continuation-in-part of my copending application S.N. 148,803, filed October 31, 1961, now abandoned.

This invention relates to an improved process for treating cellulosic materials and more particularly it relates to an improved process for the treatment of cellulosic textile materials to render them substantiallyflame-retardant.

Heretofore, considerable work has been done in the development of processes for flameproofing cellulosic materials and particularly cellulosic textiles, utilizing methylol-phosphorus polymers which have nitrogen atoms incorporated into the polymer, which polymers are well known to have excellent flame-retarding properties. In the course of this work, it has been found that it is generally not enough just to produce a cellulosic textile material which is flame retardant, but it is further desirable that this flame retardancy is retained even after repeated launderings, while at the same time, retaining the desired hand, durability, tear strength and tensile strength of the material. In this regard, the manner in which the methylol-phosphorus polymers are cured after being applied to the cellulosic textile determines to an appreciable extent Whether the final treated textile product has these desired characteristics. I

To illustrate the above, it has been found that heat curing of the methylol-phosphorus polymers after they have been deposited on the cellulosic textile, frequently results in a reduction in the tear strength and tensile strength of the treated fabric. Moreover, where the heat curing is not carefully controlled, uneven curing of the polymer occurs, often to the extent that the polymer in the interior of the fabric still has appreciable water solubility. The durability of the flame-retardant finish in such product is generally adversely affected and the cellulosic materials obtained frequently are stiff and/or boardy and, hence, not desirable.

To overcome these difliculties, in one prior art process it is proposed to effect the cure of the methylol-phosphorus polymers using ammonia, rather than heat. In this manner, the difficulties encountered in heat curing of the resin are overcome. This method has not, however, been completely satisfactory because at the time of the ammonia cure the resin is soluble in ammonia-containing solutions and is dissolved out of the fabric when ammonia solutions are used as the curing agent. Thereafter, as the dissolved resin becomes insolubilized by the ammonia in the solution, it may be redeposited on the surface of the fabric, in the form of white spots which are detrimental to the appearance of the textile material. Where gaseous ammonia is used as the curing agent, rather than an aqueous ammonia solution, there is no solubilization of the resin from the fabric but the time required to effect curing with gaseous ammonia is undesirably long and, frequently, the reaction temperatures may be sufliciently high to adversely affect the treated fabric.

It is, therefore, an object of the present invention to provide an improved process for treating cellulosic materials to render them substantially flame retardant.

A further object of the present invention is to provide an improved process for flameproofing cellulosic textiles, whereby the resulting treated textile material is made durably flame retardant and undergoes substantially no reduction in tear strength or tensile strength.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the process of the present invention includes impregnating a cellulosic material with a polymerizable composition comprising a tetrakis- (alpha-hydroxyorgano)phosphonium halide, a watersoluble, cyclic, co-polymerizable nitrogencontaining compound, a copolymerizable compound which is a carbamic acid derivative, and an acid releasing polymeriza tion catalyst, heating the thus-impregnated material at a temperature and for a period of time sufficient to partially polymerize the polymerizable composition, only to the extent that it is substantially insoluble in ammoniacontaining solutions, and, thereafter, contacting the material containing the thus-partially polymerized composition with an ammonia containing solution in an amount and for a period of time sufficient to substantially cure the composition and render it substantially water-insoluble. The cellulosic materials, such as cellulosic textiles, treated in accordance with the above process are found to be durably flame retardant, even after repeated launderings, and show no evidence of resin spotting on the surface as a result of partial dissolving of the impregnating composition during the ammonia cure. Additionally, the hand of the fabric is essentially unchanged from that of .the untreated fabric and the tear strength and tensile strength are comparable to that of untreated fabric.

More specifically, in the practice of the present method, the polymerizable composition with which the cellulosic material is impregnated is preferably an aqueous composition containing the following components in the amounts indicated.

Components: Percent by weight Tetrakis(alpha hydroxyorgano)phosphonium halide compound 10-40 Water-soluble, cyclic, copolymerizable nitrogen-containing compound 5-l5 Carbamic acid derivative 1-10 Acid releasing polymerization catalyst 1-10 Water 35-80 wherein R is selected from the group consisting of hydrogen, lower alkyls having between about 1 and about 6 carbon atoms, halogenated lower alkyls having between about 1 and about 6 carbon atoms, lower alkenyls having between about 1 and about 6 carbon atoms, halogenated lower alkenyls having between about 1 and about 6 carbon atoms, carbocyclic aryls having between about 5 and about 10 carbon atoms, halogenated aryls having between about 5 and about 10 carbon atoms, cycloalkyls having between about 3 and about 6 carbon atoms, halogenated cycloalkyls having between about 3 and about 6 carbon atoms, and X is a halogen, such as chlorine, bromine, fluorine or iodine. Typical examples and The phosphonium compounds may be used in monomer form or in a partially polymerized form, so long as they are still water-soluble. For example, tetrakis(hydroxymethyl)phosphonium chloride, which is the preferred phosphonium compound, may be heated to elfect partial polymerization before dissolving it in the solution.

Water-soluble cyclic nitrogen-containing compounds suitable for use in the present invention include the triazines and the dimethylol cyclic alkylene ureas. Typical examples of suitable triazines include the methlylol melamines, such as mono-, di-, and trirnethylol melamine; modified methylol melamines, such as the trimethyl ether of trimethylol melamine, triazines, such as dimethylol triazone; and mixtures thereof. Typical examples of suitable cyclic alkylene ureas include dimethylol ethylene urea, dimethylol propylene urea, and the like. Of these, trimethylol melamine is preferred and for this reason hereinafter primary reference will be made to this compound.

The carbamic acid derivatives which may be incorporated in the composition for use in the present method are exemplified by urea, thiourea, biuret, ethylene urea, dicyandiamide, and the like. By incorporating these compounds in the present composition, the amount of the more expensive phosphonium halide compound can be reduced, over that required when these compounds are not present. Of the compounds indicated above, the preferred are urea and thiourea and, accordingly, specific reference to these materials will be made hereinafter.

The acid releasing polymerization catalyst and bath stabilizer used in the present composition may be any suitable acid releasing catalyst which does not have an adverse effect on the copolymerization of the preferred phosphonium chloride compound with the water-soluble cyclic nitrogen containing compound and the carbamic acid derivative. Exemplary of acid releasing catalysts which may be used are strong inorganic acid salts of tertiary amines, such as tertiary amine hydrochlorides; strong inorganic acid salts of magnesium and zinc, such as magnesium chloride, zinc nitrate, magnesium sulfate, zinc sulfate, and the like; alkanol amine hydrochlorides, such as trithanolamine hydrochloride, tripropanolamine hydrochloride, tributanolamine hydrochloride, trimethylolamine hydrochloride and the like. Rather than adding the tertiary alkanolamine hydrochloride compound directly to the polymerization solution, prior to the impregnation of the textile fabric, the crresponding tertiary alkanol amines can be added to the polymerizable solution and the amine hydrochloride catalyst can be formed in situ in the polymerizable mixture by reaction of the tertiary alkano-amine with chlorine from the phosphonium chloride compound. In many instances, this in situ formation of the amine hydrochloride is preferred so that, hereinafter, in referring to the acid releasing polymerization catalyst, primary reference will be made to the use of a tertiary alkanolamine, such as triethanola-mine. It is to be appreciated, however, that this in situ generation of the catalyst is not to be confused with the in situ formation of the polymer on the cellulosic fabric treated. While in accordance with the process of the present invention, the acid releasing polymerization catalyst can be added as such to the polymerizable solution, rather than being generated in situ, the in situ formation of the methylol-phosphorus-nitrogen-containing polymer upon the cellulosic fabric substrate results in producing the advantages of the present invention.

A preferred polymerizable impregnating composition for use in the method of the present invention contains the following components in the amounts indicated.

Components: Percent by weight Tetrakis hydroxymethyl) phosphonium chloride 2332 Triethanolamine 47 Triethanolmelamine 6-9 Urea 47 Water 48-65 In addition to these components, the impregnating composition may also contain other adjuvants, such as fabric softeners, wetting agents, and the like. .Typically, when used, these adjuvants will be present in the composition in an amount up to about 3% by weight of the total impregnating composition.

In formulating the polymerizable impregnating bath for use in the present method, the non-aqueous components are added to the water, preferably in the order set forth hereinabove. Generally, agitation of the bath is desirable in order to insure that the non-aqueous components will be substantially completely dissolved in the aqueous portion of the bath. Once the impregnating bath has been formed, it is desirably maintained at a temperature below about 30 centigrade, in order to maintain maximum stability and bath life. Typical operating temperatures for the impregnating bath are between about 20 to about 30 centigrade, although it will be appreciated that in some instances both higher and lower temperatures will be used. Normally, however, temperatures substantially in excess of about 30 oentigrade are not preferred since with such temperatures, there may be a reduction in the time of useful bath life. It is to be further noted that during periods of high ambient temperatures, it may be desirable to use ice to cool the impregnating composition. In such instances, it has been found that replacement of about 15 to about 25% of the water in the impregnating bath with ice will generally be sufficient to maintain the bath temperature within the desired range without adversely affecting the concentration of the impregnating composition.

Once the polymerizable impregnating solution has been prepared, preferably in the manner indicated hereinabove, the solution may be applied to the cellulosic material, such as cellulosic textiles, in any convenient manner. For example, in the treatment of yard goods in mill apparatus, the polymerizable solution may be formulated in a padding box and the cellulosic material to be treated immersed in the solution. Thereafter, impregnation of the material is effected by passing the goods through a pad or squeeze roll or other suitable means for removing the excess solution.

It is to be noted that an important factor in the present method is the amount of resin add-on in the cellulosic materials which have been treated. Obviously, a resin add-0n which is too low may result in a product which has poor flame-retardancy and/ or a product in which the durability of the flame retardancy after repeated launderings is reduced. Moreover, it has been found that a resin add-on which is too great may result in a product which has an unsatisfactory hand, i.e., a product which is stilf and/or boardy. Accordingly, it is important that the cellulosic material treated is given a resin add-on which provides both satisfactory flame retardancy and durability, without adversely affecting the hand of the material, or in other words, that a flame retarding amount of the impregnating composition be deposited in the cellulosic material. Generally, it has been found that resin add-ons within the range of about 16 to about 24% by weight of the cellulosic material treated give satisfactory results. It will be appreciated, however, that resin add-ons which are greaterthan, or lesser than these preferred amounts may be used in some instances, depending upon the type and weight of the cellulosic material being treated.

Inasmuch, as the resin add-on of the cellulosic material treated in accordance with the present method is largely dependent upon the amount of wet pickup of the polymerizable impregnating soltuion during impregnation it will be apparent to those in the art that control of the amount of wet pickup during the impregnating step is also an important factor. Generally, it has been found that wet pickups within the range of about 65 to about 100% by weight of the fabric being treated will give a finished product having the desired resin add-on. When carrying out the impregnation on yard goods, as has been described hereinabove, the amount of wet pickup in the material may be controlled by varying the amount of pressure on the pad or squeeze roll. Desirably, the Wet pickup obtained is within the range of about 60 to about 80% by weight, thus giving a resin add-on'within the range of about 18 to about 24% by weight, and preferably is within the range of about 70 to about 75% by weight to give a resin add-on within the range of about 19 to about 21% by weight.

Once the cellulosic material has been impregnated and the wet pickup of the polymerizable solution on the material has been adjusted to the desired value, the material is partially cured by subjecting it to heat at a temperature and for a period of time sufficient to partially polymerize the polymerizable impregnant, only to the extent that it is substantially insoluble in ammonia-containing solution. Generally, this heating will be such that aldehyde groups, generated during the polymerization of the composition, will undergo substantially no reaction with the cellulose molecules of the treated material. Additionally, the extent of the polymerization will be such that there is a substantial insolubilization of the composition in ammonia-containing solutions. In order to effect this desired polymerization, it has been found that generally, the impregnated fabric should be at a temperature within the range of about 65 to about 180 centigrade and that this temperature should be maintained for a period of from about 24 hours to about seconds, the longer curing time obviously being used at the lower temperature. It is to be appreciated, however, that other curing temperatures and times may also be used which result in a similar partial polymerization of the impregnating composition to the extent that there is a substantial insolubilization of the composition in ammonia-containing solutions, provided such other tirries and temperatures used have no detrimental effects on the cellulosiotmaterial or the impregnating compositions.

The heat curing of the impregnated cellulosic material maybe carried out in any suitable equipment, asfor ex 5 ample, a loop oven, or a conventional roller type oven, or the like. With such heating equipment, the cloth temperatures used are preferably within the range of about 130 to 160 centrigrade and curing times are of from about 5 minutes to about 1 minute. 3 It is to be appreciated that in some instances it may be desirable to subject the impregnated cellulosic material to a drying operation, either prior to or simultaneously with the heat curing operation. In carrying out the drying operation prior to the heat cure, it has generally been found that the drying conditions are adjusted so as to provide a moisture content in the dried fabric of from about 5 to about 10%. In this manner, there is substantially no curing of the impregnating composition during the drying operation so that the extent of curing can be more closely controlled in the separate heat curing step. Where drying and curing are performed simultaneously, it is generally preferable that the combined operation be carried out at the lower temperatures and longer times withabove.

After the heat curing operation is completed and the desired partial polymerization of the impregnated cellulosic material is obtained, the treated cellulosic material is subjected to a chemical curing operation, using as a source of ammonia, an ammonia-containing solution. The ammonia may be supplied'for the curing operation as aqueous ammonia, including ammonium hydroxide; solutions of amino compounds containing at least two reactive hydrogen atoms per molecule, such as amines containing a primary amino group, hydrazine, alkyl-substituted hydrazine and the like; ammonium carbonate or other readily dissociated weak acid salts of ammonia, such as ammonium acetate, ammonium formate and the like. Additionally, the chemical curing of the impregnated cellulosic material may be effected, using a composition comprising a mixture of the ammonium salt of a strong acid, such as ammonium sulfate, an alkali metal carbonate, and an alkali metal bicarbonate, such as sodium carbonate and sodium bicarbonate. This mixture is dissolved in water and the impregnated cellulosic material is brought into contact with the resulting aqueous solution. Generally, for ease of operation, it is preferred to effect the chemical curing of the polymeriza'ble impregnating composition with an aqueous solution of ammonia, such as ammonium hydroxide or the aforementioned aqueous solution of the mixture of ammonium sulfate, sodium carbonate and sodium bicarbonate.

The chemical curing is carried out for a period of time sufiicient to effect substantially complete polymerization and curing of the impregnated composition, with the resulting substantially complete water insolubilization of the compositions on the cellulosic material. Obviously, the time to effect the chemical curing operation will vary, depending upon the amount of resin add-on in the treated material, as well as the nature of the cellulosic material itself. In many instances, however, curing times within the range of about 1 minute to about 5 minutes have been found to be typical. Similarly, the ammonia concentration in the chemical curing compositions may also vary, with concentrations within the range of about 1 to about 10% by Weight of the chemical curing solution being typical.

The chemical curing operation may be carried out in any suitable apparatus, as for example, a padder or in a jig. Where the padder is arranged in tandem with the curing oven, the chemical curing step may be carried out continuously. In instances where the finishing operations on the treated fabric includes scouring in the jig, however, the ammonia cure may be more conveniently carried out in the jig during the first end. Exemplary of a specific curing composition which may be used in either a padder or a jig is one cointaining the following components in the amounts indicated:

Water gallons Ammonium sulfate pounds 50 Sodium carbonate ...do 30 Sodium bicarbonate do 50 After effecting the chemical curing of the impregnated fabric with this composition, a hold time of at least about 1 minute is desirable before subsequent processing operations, such as scouring, are carried out.

Following the chemical cure of the cellulosic material, the treated fabric is preferably scoured or washed to remove any unpolymerized material from the fabric. Typically, the scouring operation may 'be effected using any conventional scouring process, such as rope scouring, continuous open Width scouring, jig scouring, and the like. The scouring may conveniently be carried out using an aqueous soap solution containing small amounts of sodium carbonate and sodium perborate. The scouring or washing operation is preferably followed by a drying step wherein the treated fabric is dried in a conventional manner, after which the fabric may be subjected to any desired finishing operation such as shrink proofing, calendering, and the like.

The cellulosic materials treated in accordance with the procedures which have been described hereinabove are found to be durably flame retardant, even after numerous launderings. Additionally, these materials are found to have a tear strength, tensile strength and hand substantially unchanged from those of untreated materials. Moreover, the treated cellulosic textiles are found to be further characterized by the absence of deposits of resinous material on the surface thereof, which deposits have characterized textile materials which have been processed by prior art methods which utilize only a chemical curing operation.

In order that those skilled in the art may better understand the present invention and the manner in which it may be practiced, the following specific examples are given. It is to be appreciated that these examples are intended to be exemplary of the present invention and are not to be taken as limitations thereof. In these examples, unless otherwise indicated, temperatures are in degrees centigrade and quantities are in percents by weight. Additionally, the flame retardancies reported were determined in accordance with the procedure of the American Association of Textile Chemists and Colorists, Test AATCC Base 34-1952.

EXAMPLE 1 An aqueous polymerizable impregnating solution was prepared containing the following components in the amounts indicated.

Component: Percent by weight Tetrakis (hydroxymethyl phosphonium chloride (80% aqueous solution) 27.3 Trimethylolmelamine 7.3 Urea 4.5

Triethanolamine 4.2 Polyethylene softener 3.0 Water 53.7

5 ounce cotton sheeting was padded through the above bath and a wet pick-up of 95% was obtained. The thusimpregnated cloth was then dried for 1.1 minutes at 93 centigrade. Thereafter, samples of the cloth were cured for 1.5 minutes at different temperatures and some of the heat cured samples were given an ammonia cure, using the following aqueous ammonia solution.

Component: Percent by weight (NH 80 7 Soda ash 3 Water 90 The treated samples were then subjected to the standard char test, both initially and after 15 boil cycles. Using these procedures, the results obtained were as follows:

Char length, in inches Sample Heat Cure Ammonia Initial After 15 boil cycles 1.5 min. at, 138 0. Yes 3.0 5. 1.5 min. at l38 No 3.3 1.5 min. at 149 0 Yes 3. 6 3. 1.5 min. at 149 C No r- 3. 3 1.5 min. at 160 0 Yes 3.8 4.9 1.5 min. at 160 o No 5.0 2 7. 5

1 Burns 2 Fails EXAMPLE 2 Component: Percent by Weight Tetrakis (hydroxymethyl)phosphonium c h l oride (80% aqueous solution) 30.0 Trimethylolmelamine 6.0 Triethanolamine 2.4 Thiourea 5.0

Water 56.6

After padding through this bath to a wet pick-up of 95%, the cotton sheeting was dried for 4 minutes at 93 centigrade. Thereafter, it was padded through a 10% aqueous ammonia solution, dried and subjected to the standard char test. Using this procedure, it was found that the initial char length, in inches, was 4.5 and that after 15 boil cycles the cloth burned. Additionally, it was noted that there were numerous resin spots on the fabric.

From the above examples, it is seen that the cellulosic textiles treated in accordance with the process of the present invention are durably flame-retardant. Additionally, it was found that the tear strength, tensile strength and hand of these materials were substantially unchanged and that there were no resin deposits formed on the treated fabrics.

While there have been described various embodiments of the invention, the compositions and methods described -are not intended to be understood as limiting the scope of the invention, as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. A process for preparing flame-retardant cellulosic materials which comprises impregnating a cellulosic material with a polymerizable composition consisting essentially of a tetrakis (u-hydroxyorgano)phosphonium halide, a water-soluble cyclic copolymerizable nitrogencontaining compound selected from the group consisting of triazines and dimethylol cyclic alkylene ureas, a copolymerizable compound which is a carbamic acid derivative, and an acid releasing polymerization catalyst, heating the thus-impregnated material at a temperature and for a period of time sufficient to partially polymerize the polymerizable composition only to the extent that it is substantially insoluble in ammonia-containing solutions, and thereafter, contacting the material containing the thus-partially polymerized composition with an ammoniacontaining solution, in an amount and for a period of time sufficient to substantially cure the composition and render it substantially water insoluble.

2. A process for preparing a flame-retardant cellulosic material which comprises impregnating the cellulosic material with a polymerizable composition consisting essentially of a water-soluble cyclic copolymerizable nitrogencontaining compound selected from the group consisting of triazines and dimethylol cyclic alkylene ureas, a copolymerizable compound selected from the group consisting of urea and thiourea, an acid releasing polymerization catalyst, and a tetrakis (a-hydroxyorgano)phosphonium halide having the formula:

wherein R is selected from the group consisting of hydrogen, lower alkyls having between 1 and about 6 carbon atoms, halogenated lower alkyls having between about 1 and about 6 carbon atoms, lower alkenyls having between about 1 and about 6 carbon atoms, halogenated lower alkenyls having between about 1 and about 6 can bon atoms, carbocyclic aryls having between about 5 and about 10 carbon atoms, halogenated carbocyclic aryls having between about 5 and about 10 carbon atoms, cycloalkyls having between about 3 and about 6 carbon atoms, and halogenated cycloalkyls having between about 3 and about 6 carbon atoms, and X is halogen, heating the thus-impregnated material at a temperature and for a P iQd Qf time sufficient to partially polymerize the polymerizable composition only to the extent that it is substantially insoluble in ammonia-containing solutions and thereafter contacting the material containing the thus-partially polymerized composition with an ammoniacontaining solution, in an amount and for a period of time sufficient to substantially cure the composition and render it substantially water-insoluble.

3. A process for preparing a flame-retardant cellulosic textile material which comprises impregnating the cellulosic textile material with a polymerizable composition consisting essentially of tetrakis(hydroxymethyl)phosphonium chloride, trimethylolmelamine, a copolymerizable compound selected from the group consisting of urea and thiourea, and an acid releasing polymerization catalyst, heating the thus-impregnated material at a temperature and for a period of time sulficient to partially polymerize the polymerizable composition only to the extent that it is substantially insoluble in ammonia-containing solutions, and thereafter, contacting the material containing the thus-partially polymerized composition with an aqueous solution containing ammonia in an amount and for a period of time suficient to substantially cure the composition and render it substantially waterinsoluble.

4. The process as claimed in claim 3 wherein the tetrakis(hydroxymethyl)phosphonium chloride is present in an amount within the range of about 10 to 40 percent by weight, the trimethylolmelamine is present in amounts within the range of about 5 to about 15 percent by weight, the copolymerizable compound selected from the group consisting of urea or thiourea is present in an amount within the range of about 1 to about 10 percent by Weight, the acid releasing polymerization catalyst is present in an amount within the range of about 1 to about 10 percent by weight, and there is present about to about percent by weight of water.

5. The process as claimed in claim 4 wherein the acid releasing polymerization catalyst is triethanolamine.

6. The process as claimed in claim 3 wherein the partial polymerization of the polymerizable impregnating composition is effected by heating the impregnated cellulosic textile material so that it is at a temperature within the range of about 65 to about centigrade for a period of time within the range of about 24 hours to about 10 seconds.

7. The process as claimed in claim 6 wherein the final cure of the partially polymerized impregnating composition in the cellulosic textile material is effected by contacting the material with an aqueous, ammonia-containing solution.

References Cited by the Examiner UNITED STATES PATENTS 2,772,188 11/1956 Reeves et al 117-136 2,809,941 10/1957 Reeves et al 117136 X 2,922,726 1/1960 Moretti et a1 117136 X 2,983,623 5/1961 Coates 117-62 3,101,279 8/1963 Wagner et al. 117137 WILLIAM D. MARTIN, Primary Examiner. T. G, DAVIS, Assistant Examiner,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,310 ,420 March 21 1967 George M. Wagner It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 27, for "triazines" read triazones line 55, for "trithanolamine" read triethanolamine line 60,' for "cTresponding" read corresponding line 63, for "a1kano-amine"'read alkanol-amine column 5, line 8, for "soltuion" read solution line 57', for "centrigrade" read centigrade column 6, line 51, for "cointaining" read containing column 7, line 68, after "EXAMPLE 2" insert The procedure of Example 1 was repeated using the following impregnating bath:

Signed and sealed this 17th day of December 1968.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR PREPARING FLAME-RETARDANT CELLULOSIC MATERIALS WHICH COMPRISES IMPREGNATING A CELLULOSIC MATERIAL WITH A POLYMERIZABLE COMPOSITION CONSISTING ESSENTIALLY OF A TETRAKIS (A-HYDROXYORGANO) PHOSPHONIUM HALIDE, A WATER-SOLUBLE CYCLIC COPOLYMERIZABLE NITROGENCONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF TRIAZINES AND DIMETHYOL CYCLIC ALKYLENE UREAS, A COPOLYMERIZABLE COMPOUND WHICH IS A CARBAMIC ACID DERIVATIVE, AND AN ACID RELEASING POLYMERIZATION CATALYST, HEATING THE THUS-IMPREGNATED MATERIAL AT A TEMPERATURE AND FOR A PERIOD OF TIME SUFFICIENT TO PARTIALLY POLYMERIZE THE POLYMERIZABLE COMPOSITION ONLY TO THE EXTENT THAT IT IS SUBSTANTIALLY INSOLUBLE IN AMMONIA-CONTAINING SOLUTIONS, AND THEREAFTER, CONTACTING THE MATERIAL CONTAINING THE THUS-PARTIALLY POLYMERIZED COMPOSITION WITH AN AMMONIACONTAINING SOLUTION, IN AN AMOUNT FOR A PERIOD OF TIME SUFFICIENT TO SUBSTANTIALLY CURE THE COMPOSITION AND RENDER IT SUBSTANTIALLY WATER INSOLUBLE. 